1. Field of the Invention
The present invention relates to a container inspection apparatus, and more particularly to an apparatus for optically inspecting sealing performance of a closure of a container such as a bottle filled with an effervescent beverage. The effervescent beverage includes beer, carbonated drinks, and the like.
2. Description of the Prior Art
As an apparatus for inspecting sealing performance of a closure of a container, there has been known an apparatus which comprises means for causing a beverage to effervesce by applying ultrasonic vibration to the bottom of the container, and means for imaging liquid surface in the container and judging the container as a defective container which is not properly sealed when a large effervescent portion is detected at the liquid surface in the container. The conventional means for causing a beverage to effervesce comprises a net conveyor provided in a water tank and conveying containers while they are submerged in water in the water tank, and ultrasonic transducers provided at the bottom of the water tank. The ultrasonic transducers apply ultrasonic vibration to the bottoms of the containers on the net conveyor through water in the water tank. The containers are densely placed on the net conveyor in a staggered arrangement. The ultrasonic transducers are arranged at intervals to prevent mutual interference and in a plurality of rows which extend in a direction perpendicular to the traveling direction of the containers.
However, in the conventional means for causing a beverage to effervesce, the intensities of ultrasonic vibrations are not uniform in an entire area where the ultrasonic transducers are arranged, and hence some defective containers cannot be detected because of their small degrees of effervescence. Further, since the energy of ultrasonic vibration which is applied to the container per unit time is small, considerable time is required to allow a beverage to effervesce, thus requiring a large installation area for the container inspection apparatus.